/src/git/wrapper.c

Source
/*
 * Various trivial helper wrappers around standard functions
 */

#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "abspath.h"
#include "parse.h"
#include "gettext.h"
#include "strbuf.h"
#include "trace2.h"

#ifdef HAVE_RTLGENRANDOM
/* This is required to get access to RtlGenRandom. */
#define SystemFunction036 NTAPI SystemFunction036
#include <ntsecapi.h>
#undef SystemFunction036
#endif

static int memory_limit_check(size_t size, int gentle)
{
  static size_t limit = 0;
  if (!limit) {
    limit = git_env_ulong("GIT_ALLOC_LIMIT", 0);
    if (!limit)
      limit = SIZE_MAX;
  }
  if (size > limit) {
    if (gentle) {
      error("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
            (uintmax_t)size, (uintmax_t)limit);
      return -1;
    } else
      die("attempting to allocate %"PRIuMAX" over limit %"PRIuMAX,
          (uintmax_t)size, (uintmax_t)limit);
  }
  return 0;
}

char *xstrdup(const char *str)
{
  char *ret = strdup(str);
  if (!ret)
    die("Out of memory, strdup failed");
  return ret;
}

static void *do_xmalloc(size_t size, int gentle)
{
  void *ret;

  if (memory_limit_check(size, gentle))
    return NULL;
  ret = malloc(size);
  if (!ret && !size)
    ret = malloc(1);
  if (!ret) {
    if (!gentle)
      die("Out of memory, malloc failed (tried to allocate %lu bytes)",
          (unsigned long)size);
    else {
      error("Out of memory, malloc failed (tried to allocate %lu bytes)",
            (unsigned long)size);
      return NULL;
    }
  }
#ifdef XMALLOC_POISON
  memset(ret, 0xA5, size);
#endif
  return ret;
}

void *xmalloc(size_t size)
{
  return do_xmalloc(size, 0);
}

static void *do_xmallocz(size_t size, int gentle)
{
  void *ret;
  if (unsigned_add_overflows(size, 1)) {
    if (gentle) {
      error("Data too large to fit into virtual memory space.");
      return NULL;
    } else
      die("Data too large to fit into virtual memory space.");
  }
  ret = do_xmalloc(size + 1, gentle);
  if (ret)
    ((char*)ret)[size] = 0;
  return ret;
}

void *xmallocz(size_t size)
{
  return do_xmallocz(size, 0);
}

void *xmallocz_gently(size_t size)
{
  return do_xmallocz(size, 1);
}

/*
 * xmemdupz() allocates (len + 1) bytes of memory, duplicates "len" bytes of
 * "data" to the allocated memory, zero terminates the allocated memory,
 * and returns a pointer to the allocated memory. If the allocation fails,
 * the program dies.
 */
void *xmemdupz(const void *data, size_t len)
{
  return memcpy(xmallocz(len), data, len);
}

char *xstrndup(const char *str, size_t len)
{
  const char *p = memchr(str, '\0', len);
  return xmemdupz(str, p ? p - str : len);
}

int xstrncmpz(const char *s, const char *t, size_t len)
{
  int res = strncmp(s, t, len);
  if (res)
    return res;
  return s[len] == '\0' ? 0 : 1;
}

void *xrealloc(void *ptr, size_t size)
{
  void *ret;

  if (!size) {
    free(ptr);
    return xmalloc(0);
  }

  memory_limit_check(size, 0);
  ret = realloc(ptr, size);
  if (!ret)
    die("Out of memory, realloc failed");
  return ret;
}

void *xcalloc(size_t nmemb, size_t size)
{
  void *ret;

  if (unsigned_mult_overflows(nmemb, size))
    die("data too large to fit into virtual memory space");

  memory_limit_check(size * nmemb, 0);
  ret = calloc(nmemb, size);
  if (!ret && (!nmemb || !size))
    ret = calloc(1, 1);
  if (!ret)
    die("Out of memory, calloc failed");
  return ret;
}

void xsetenv(const char *name, const char *value, int overwrite)
{
  if (setenv(name, value, overwrite))
    die_errno(_("could not setenv '%s'"), name ? name : "(null)");
}

/**
 * xopen() is the same as open(), but it die()s if the open() fails.
 */
int xopen(const char *path, int oflag, ...)
{
  mode_t mode = 0;
  va_list ap;

  /*
   * va_arg() will have undefined behavior if the specified type is not
   * compatible with the argument type. Since integers are promoted to
   * ints, we fetch the next argument as an int, and then cast it to a
   * mode_t to avoid undefined behavior.
   */
  va_start(ap, oflag);
  if (oflag & O_CREAT)
    mode = va_arg(ap, int);
  va_end(ap);

  for (;;) {
    int fd = open(path, oflag, mode);
    if (fd >= 0)
      return fd;
    if (errno == EINTR)
      continue;

    if ((oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
      die_errno(_("unable to create '%s'"), path);
    else if ((oflag & O_RDWR) == O_RDWR)
      die_errno(_("could not open '%s' for reading and writing"), path);
    else if ((oflag & O_WRONLY) == O_WRONLY)
      die_errno(_("could not open '%s' for writing"), path);
    else
      die_errno(_("could not open '%s' for reading"), path);
  }
}

static int handle_nonblock(int fd, short poll_events, int err)
{
  struct pollfd pfd;

  if (err != EAGAIN && err != EWOULDBLOCK)
    return 0;

  pfd.fd = fd;
  pfd.events = poll_events;

  /*
   * no need to check for errors, here;
   * a subsequent read/write will detect unrecoverable errors
   */
  poll(&pfd, 1, -1);
  return 1;
}

/*
 * xread() is the same a read(), but it automatically restarts read()
 * operations with a recoverable error (EAGAIN and EINTR). xread()
 * DOES NOT GUARANTEE that "len" bytes is read even if the data is available.
 */
ssize_t xread(int fd, void *buf, size_t len)
{
  ssize_t nr;
  if (len > MAX_IO_SIZE)
    len = MAX_IO_SIZE;
  while (1) {
    nr = read(fd, buf, len);
    if (nr < 0) {
      if (errno == EINTR)
        continue;
      if (handle_nonblock(fd, POLLIN, errno))
        continue;
    }
    return nr;
  }
}

/*
 * xwrite() is the same a write(), but it automatically restarts write()
 * operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT
 * GUARANTEE that "len" bytes is written even if the operation is successful.
 */
ssize_t xwrite(int fd, const void *buf, size_t len)
{
  ssize_t nr;
  if (len > MAX_IO_SIZE)
    len = MAX_IO_SIZE;
  while (1) {
    nr = write(fd, buf, len);
    if (nr < 0) {
      if (errno == EINTR)
        continue;
      if (handle_nonblock(fd, POLLOUT, errno))
        continue;
    }

    return nr;
  }
}

/*
 * xpread() is the same as pread(), but it automatically restarts pread()
 * operations with a recoverable error (EAGAIN and EINTR). xpread() DOES
 * NOT GUARANTEE that "len" bytes is read even if the data is available.
 */
ssize_t xpread(int fd, void *buf, size_t len, off_t offset)
{
  ssize_t nr;
  if (len > MAX_IO_SIZE)
    len = MAX_IO_SIZE;
  while (1) {
    nr = pread(fd, buf, len, offset);
    if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
      continue;
    return nr;
  }
}

ssize_t read_in_full(int fd, void *buf, size_t count)
{
  char *p = buf;
  ssize_t total = 0;

  while (count > 0) {
    ssize_t loaded = xread(fd, p, count);
    if (loaded < 0)
      return -1;
    if (loaded == 0)
      return total;
    count -= loaded;
    p += loaded;
    total += loaded;
  }

  return total;
}

ssize_t write_in_full(int fd, const void *buf, size_t count)
{
  const char *p = buf;
  ssize_t total = 0;

  while (count > 0) {
    ssize_t written = xwrite(fd, p, count);
    if (written < 0)
      return -1;
    if (!written) {
      errno = ENOSPC;
      return -1;
    }
    count -= written;
    p += written;
    total += written;
  }

  return total;
}

ssize_t writev_in_full(int fd, struct iovec *iov, int iovcnt)
{
  ssize_t total_written = 0;

  while (iovcnt) {
    ssize_t bytes_written = writev(fd, iov, iovcnt);
    if (bytes_written < 0) {
      if (errno == EINTR || errno == EAGAIN)
        continue;
      return -1;
    }
    if (!bytes_written) {
      errno = ENOSPC;
      return -1;
    }

    total_written += bytes_written;

    /*
     * We first need to discard any iovec entities that have been
     * fully written.
     */
    while (iovcnt && (size_t)bytes_written >= iov->iov_len) {
      bytes_written -= iov->iov_len;
      iov++;
      iovcnt--;
    }

    /*
     * Finally, we need to adjust the last iovec in case we have
     * performed a partial write.
     */
    if (iovcnt && bytes_written) {
      iov->iov_base = (char *) iov->iov_base + bytes_written;
      iov->iov_len -= bytes_written;
    }
  }

  return total_written;
}

ssize_t pread_in_full(int fd, void *buf, size_t count, off_t offset)
{
  char *p = buf;
  ssize_t total = 0;

  while (count > 0) {
    ssize_t loaded = xpread(fd, p, count, offset);
    if (loaded < 0)
      return -1;
    if (loaded == 0)
      return total;
    count -= loaded;
    p += loaded;
    total += loaded;
    offset += loaded;
  }

  return total;
}

int xdup(int fd)
{
  int ret = dup(fd);
  if (ret < 0)
    die_errno("dup failed");
  return ret;
}

/**
 * xfopen() is the same as fopen(), but it die()s if the fopen() fails.
 */
FILE *xfopen(const char *path, const char *mode)
{
  for (;;) {
    FILE *fp = fopen(path, mode);
    if (fp)
      return fp;
    if (errno == EINTR)
      continue;

    if (*mode && mode[1] == '+')
      die_errno(_("could not open '%s' for reading and writing"), path);
    else if (*mode == 'w' || *mode == 'a')
      die_errno(_("could not open '%s' for writing"), path);
    else
      die_errno(_("could not open '%s' for reading"), path);
  }
}

FILE *xfdopen(int fd, const char *mode)
{
  FILE *stream = fdopen(fd, mode);
  if (!stream)
    die_errno("Out of memory? fdopen failed");
  return stream;
}

FILE *fopen_for_writing(const char *path)
{
  FILE *ret = fopen(path, "w");

  if (!ret && errno == EPERM) {
    if (!unlink(path))
      ret = fopen(path, "w");
    else
      errno = EPERM;
  }
  return ret;
}

static void warn_on_inaccessible(const char *path)
{
  warning_errno(_("unable to access '%s'"), path);
}

int warn_on_fopen_errors(const char *path)
{
  if (errno != ENOENT && errno != ENOTDIR) {
    warn_on_inaccessible(path);
    return -1;
  }

  return 0;
}

FILE *fopen_or_warn(const char *path, const char *mode)
{
  FILE *fp = fopen(path, mode);

  if (fp)
    return fp;

  warn_on_fopen_errors(path);
  return NULL;
}

int xmkstemp(char *filename_template)
{
  return xmkstemp_mode(filename_template, 0600);
}

/* Adapted from libiberty's mkstemp.c. */

#undef TMP_MAX
#define TMP_MAX 16384

/*
 * Returns -1 on error, 0 if it created a directory, or an open file
 * descriptor to the created regular file.
 */
static int git_mkdstemps_mode(char *pattern, int suffix_len, int mode, bool dir)
{
  static const char letters[] =
    "abcdefghijklmnopqrstuvwxyz"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "0123456789";
  static const int num_letters = ARRAY_SIZE(letters) - 1;
  static const char x_pattern[] = "XXXXXX";
  static const int num_x = ARRAY_SIZE(x_pattern) - 1;
  char *filename_template;
  size_t len;
  int fd, count;

  len = strlen(pattern);

  if (len < num_x + suffix_len) {
    errno = EINVAL;
    return -1;
  }

  if (strncmp(&pattern[len - num_x - suffix_len], x_pattern, num_x)) {
    errno = EINVAL;
    return -1;
  }

  /*
   * Replace pattern's XXXXXX characters with randomness.
   * Try TMP_MAX different filenames.
   */
  filename_template = &pattern[len - num_x - suffix_len];
  for (count = 0; count < TMP_MAX; ++count) {
    int i;
    uint64_t v;
    if (csprng_bytes(&v, sizeof(v), 0) < 0)
      return error_errno("unable to get random bytes for temporary file");

    /* Fill in the random bits. */
    for (i = 0; i < num_x; i++) {
      filename_template[i] = letters[v % num_letters];
      v /= num_letters;
    }

    if (dir)
      fd = mkdir(pattern, mode);
    else
      fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
    if (fd >= 0)
      return fd;
    /*
     * Fatal error (EPERM, ENOSPC etc).
     * It doesn't make sense to loop.
     */
    if (errno != EEXIST)
      break;
  }
  /* We return the null string if we can't find a unique file name.  */
  pattern[0] = '\0';
  return -1;
}

char *git_mkdtemp(char *pattern)
{
  return git_mkdstemps_mode(pattern, 0, 0700, true) ? NULL : pattern;
}

int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
{
  return git_mkdstemps_mode(pattern, suffix_len, mode, false);
}

int git_mkstemp_mode(char *pattern, int mode)
{
  /* mkstemp is just mkstemps with no suffix */
  return git_mkstemps_mode(pattern, 0, mode);
}

int xmkstemp_mode(char *filename_template, int mode)
{
  int fd;
  char origtemplate[PATH_MAX];
  strlcpy(origtemplate, filename_template, sizeof(origtemplate));

  fd = git_mkstemp_mode(filename_template, mode);
  if (fd < 0) {
    int saved_errno = errno;
    const char *nonrelative_template;

    if (!filename_template[0])
      filename_template = origtemplate;

    nonrelative_template = absolute_path(filename_template);
    errno = saved_errno;
    die_errno("Unable to create temporary file '%s'",
      nonrelative_template);
  }
  return fd;
}

/*
 * Some platforms return EINTR from fsync. Since fsync is invoked in some
 * cases by a wrapper that dies on failure, do not expose EINTR to callers.
 */
static int fsync_loop(int fd)
{
  int err;

  do {
    err = fsync(fd);
  } while (err < 0 && errno == EINTR);
  return err;
}

int git_fsync(int fd, enum fsync_action action)
{
  switch (action) {
  case FSYNC_WRITEOUT_ONLY:
    trace2_counter_add(TRACE2_COUNTER_ID_FSYNC_WRITEOUT_ONLY, 1);

#ifdef __APPLE__
    /*
     * On macOS, fsync just causes filesystem cache writeback but
     * does not flush hardware caches.
     */
    return fsync_loop(fd);
#endif

#ifdef HAVE_SYNC_FILE_RANGE
    /*
     * On linux 2.6.17 and above, sync_file_range is the way to
     * issue a writeback without a hardware flush. An offset of
     * 0 and size of 0 indicates writeout of the entire file and the
     * wait flags ensure that all dirty data is written to the disk
     * (potentially in a disk-side cache) before we continue.
     */

    return sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WAIT_BEFORE |
             SYNC_FILE_RANGE_WRITE |
             SYNC_FILE_RANGE_WAIT_AFTER);
#endif

#ifdef fsync_no_flush
    return fsync_no_flush(fd);
#endif

    errno = ENOSYS;
    return -1;

  case FSYNC_HARDWARE_FLUSH:
    trace2_counter_add(TRACE2_COUNTER_ID_FSYNC_HARDWARE_FLUSH, 1);

    /*
     * On macOS, a special fcntl is required to really flush the
     * caches within the storage controller. As of this writing,
     * this is a very expensive operation on Apple SSDs.
     */
#ifdef __APPLE__
    return fcntl(fd, F_FULLFSYNC);
#else
    return fsync_loop(fd);
#endif
  default:
    BUG("unexpected git_fsync(%d) call", action);
  }
}

static int warn_if_unremovable(const char *op, const char *file, int rc)
{
  int err;
  if (!rc || errno == ENOENT)
    return 0;
  err = errno;
  warning_errno("unable to %s '%s'", op, file);
  errno = err;
  return rc;
}

int unlink_or_msg(const char *file, struct strbuf *err)
{
  int rc = unlink(file);

  assert(err);

  if (!rc || errno == ENOENT)
    return 0;

  strbuf_addf(err, "unable to unlink '%s': %s",
        file, strerror(errno));
  return -1;
}

int unlink_or_warn(const char *file)
{
  return warn_if_unremovable("unlink", file, unlink(file));
}

int rmdir_or_warn(const char *file)
{
  return warn_if_unremovable("rmdir", file, rmdir(file));
}

static int access_error_is_ok(int err, unsigned flag)
{
  return (is_missing_file_error(err) ||
    ((flag & ACCESS_EACCES_OK) && err == EACCES));
}

int access_or_warn(const char *path, int mode, unsigned flag)
{
  int ret = access(path, mode);
  if (ret && !access_error_is_ok(errno, flag))
    warn_on_inaccessible(path);
  return ret;
}

int access_or_die(const char *path, int mode, unsigned flag)
{
  int ret = access(path, mode);
  if (ret && !access_error_is_ok(errno, flag))
    die_errno(_("unable to access '%s'"), path);
  return ret;
}

char *xgetcwd(void)
{
  struct strbuf sb = STRBUF_INIT;
  if (strbuf_getcwd(&sb))
    die_errno(_("unable to get current working directory"));
  return strbuf_detach(&sb, NULL);
}

int xsnprintf(char *dst, size_t max, const char *fmt, ...)
{
  va_list ap;
  int len;

  va_start(ap, fmt);
  len = vsnprintf(dst, max, fmt, ap);
  va_end(ap);

  if (len < 0)
    die(_("unable to format message: %s"), fmt);
  if (len >= max)
    BUG("attempt to snprintf into too-small buffer");
  return len;
}

void write_file_buf(const char *path, const char *buf, size_t len)
{
  int fd = xopen(path, O_WRONLY | O_CREAT | O_TRUNC, 0666);
  if (write_in_full(fd, buf, len) < 0)
    die_errno(_("could not write to '%s'"), path);
  if (close(fd))
    die_errno(_("could not close '%s'"), path);
}

void write_file(const char *path, const char *fmt, ...)
{
  va_list params;
  struct strbuf sb = STRBUF_INIT;

  va_start(params, fmt);
  strbuf_vaddf(&sb, fmt, params);
  va_end(params);

  strbuf_complete_line(&sb);

  write_file_buf(path, sb.buf, sb.len);
  strbuf_release(&sb);
}

void sleep_millisec(int millisec)
{
  poll(NULL, 0, millisec);
}

int xgethostname(char *buf, size_t len)
{
  /*
   * If the full hostname doesn't fit in buf, POSIX does not
   * specify whether the buffer will be null-terminated, so to
   * be safe, do it ourselves.
   */
  int ret = gethostname(buf, len);
  if (!ret)
    buf[len - 1] = 0;
  return ret;
}

int is_missing_file(const char *filename)
{
  struct stat st;

  if (stat(filename, &st) < 0) {
    if (errno == ENOENT)
      return 1;
    die_errno(_("could not stat %s"), filename);
  }

  return 0;
}

int is_empty_or_missing_file(const char *filename)
{
  struct stat st;

  if (stat(filename, &st) < 0) {
    if (errno == ENOENT)
      return 1;
    die_errno(_("could not stat %s"), filename);
  }

  return !st.st_size;
}

int open_nofollow(const char *path, int flags)
{
#ifdef O_NOFOLLOW
  int ret = open(path, flags | O_NOFOLLOW);
  /*
   * NetBSD sets errno to EFTYPE when path is a symlink. The only other
   * time this errno occurs when O_REGULAR is used. Since we don't use
   * it anywhere we can avoid an lstat here. FreeBSD does the same with
   * EMLINK.
   */
# ifdef __NetBSD__
#  define SYMLINK_ERRNO EFTYPE
# elif defined(__FreeBSD__)
#  define SYMLINK_ERRNO EMLINK
# endif
# if SYMLINK_ERRNO
  if (ret < 0 && errno == SYMLINK_ERRNO) {
    errno = ELOOP;
    return -1;
  }
#  undef SYMLINK_ERRNO
# endif
  return ret;
#else
  struct stat st;
  if (lstat(path, &st) < 0)
    return -1;
  if (S_ISLNK(st.st_mode)) {
    errno = ELOOP;
    return -1;
  }
  return open(path, flags);
#endif
}

int csprng_bytes(void *buf, size_t len, MAYBE_UNUSED unsigned flags)
{
#if defined(HAVE_ARC4RANDOM) || defined(HAVE_ARC4RANDOM_LIBBSD)
  /* This function never returns an error. */
  arc4random_buf(buf, len);
  return 0;
#elif defined(HAVE_GETRANDOM)
  ssize_t res;
  char *p = buf;
  while (len) {
    res = getrandom(p, len, 0);
    if (res < 0)
      return -1;
    len -= res;
    p += res;
  }
  return 0;
#elif defined(HAVE_GETENTROPY)
  int res;
  char *p = buf;
  while (len) {
    /* getentropy has a maximum size of 256 bytes. */
    size_t chunk = len < 256 ? len : 256;
    res = getentropy(p, chunk);
    if (res < 0)
      return -1;
    len -= chunk;
    p += chunk;
  }
  return 0;
#elif defined(HAVE_RTLGENRANDOM)
  if (!RtlGenRandom(buf, len))
    return -1;
  return 0;
#elif defined(HAVE_OPENSSL_CSPRNG)
  switch (RAND_pseudo_bytes(buf, len)) {
  case 1:
    return 0;
  case 0:
    if (flags & CSPRNG_BYTES_INSECURE)
      return 0;
    errno = EIO;
    return -1;
  default:
    errno = ENOTSUP;
    return -1;
  }
#else
  ssize_t res;
  char *p = buf;
  int fd, err;
  fd = open("/dev/urandom", O_RDONLY);
  if (fd < 0)
    return -1;
  while (len) {
    res = xread(fd, p, len);
    if (res < 0) {
      err = errno;
      close(fd);
      errno = err;
      return -1;
    }
    len -= res;
    p += res;
  }
  close(fd);
  return 0;
#endif
}

uint32_t git_rand(unsigned flags)
{
  uint32_t result;

  if (csprng_bytes(&result, sizeof(result), flags) < 0)
    die(_("unable to get random bytes"));

  return result;
}

static void mmap_limit_check(size_t length)
{
  static size_t limit = 0;
  if (!limit) {
    limit = git_env_ulong("GIT_MMAP_LIMIT", 0);
    if (!limit)
      limit = SIZE_MAX;
  }
  if (length > limit)
    die(_("attempting to mmap %"PRIuMAX" over limit %"PRIuMAX),
        (uintmax_t)length, (uintmax_t)limit);
}

void *xmmap_gently(void *start, size_t length,
      int prot, int flags, int fd, off_t offset)
{
  void *ret;

  mmap_limit_check(length);
  ret = mmap(start, length, prot, flags, fd, offset);
  if (ret == MAP_FAILED && !length)
    ret = NULL;
  return ret;
}

const char *mmap_os_err(void)
{
  static const char blank[] = "";
#if defined(__linux__)
  if (errno == ENOMEM) {
    /* this continues an existing error message: */
    static const char enomem[] =
", check sys.vm.max_map_count and/or RLIMIT_DATA";
    return enomem;
  }
#endif /* OS-specific bits */
  return blank;
}

void *xmmap(void *start, size_t length,
  int prot, int flags, int fd, off_t offset)
{
  void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
  if (ret == MAP_FAILED)
    die_errno(_("mmap failed%s"), mmap_os_err());
  return ret;
}

Coverage Report

Created: 2026-03-31 06:24